Since bats hunt almost exclusively using echolocation, they could be …

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Bats hunt prey relying on a single sense: hearing or, more specifically, echolocation. Bats have the ability to emit a high-pitched noise that will bounce off objects and return to the bat, where its brain interprets the signals, allowing for accurate hunting. It's not clear what effect human-generated noise pollution has on this ability, although this could significantly affect bat population dynamics.

New work published in the latest edition of The Journal of Experimental Biology looks at whether bats are willing to forage in areas with noise levels akin to highways. Researchers from the Max Planck Institute for Ornithology in Germany (yes, we know bats aren't birds—we didn't name the Institute) examined the effect of different kinds of noise on bat's ability to detect and forage for mealworms. The experimental setup consisted of a soundproof room with the back half divided in two, where mealworms were allowed to rustle around as an all-you-can-eat buffet for the bats that occupied the room. The subjects of the experiments were a group of young, male greater mouse-eared bats (Myotis myotis).

In the control portion of the experiment, there was no noise outside that produced by the bats and mealworms. In this setup, the researchers noted that the bats split their time evenly between the two back halves of the room and were able to find the mealworms without trouble. As a first test, the researchers piped true white noise into one half of the hunting area. They found that the harsh buzzing noise drove the bats to forage on the quiet side of the room—80 percent of bats the hunting was done in the quiet area.

To mimic the effect of of man-made noise, the researchers made a recording of traffic sounds 15 meters from a busy road. When this noise was introduced, the bats preferred the quiet area, with just under 40 percent of the hunting occurring in the noisy area (as compared to only 20 percent in the white noise case). Finally, the researchers examined the effect of a natural noise on the bats' hunting preferences using a simulation of the noise made by high winds rattling reed beds. It turns out that the bats did not like this noise either, and preferred to forage in the quiet area once again.

The researchers conclude that man-made noise does interfere with bats' ability to locate prey and feed, but no more than naturally occurring noises that the bats regularly encounter. The authors admit that the work does not make it entirely clear how the man-made noise interferes with bat's ability to forage. They plan to continue experimenting with the goal of finding a way of producing bat-friendly road construction guidelines that will protect endangered species in a noisy world.

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Matt Ford
Matt is a contributing writer at Ars Technica, focusing on physics, astronomy, chemistry, mathematics, and engineering. When he's not writing, he works on realtime models of large-scale engineering systems. Emailzeotherm@gmail.com//Twitter@zeotherm